Error while creating a registered connection

  • Good day!

    we are using a Quectel chip to connect to the NB-IoT network. Now we are making first attempts on the connection. We proceeded step by step according to the “NarrowBand IoT Quick Start Guide” and came till here:
    #Now data is sent through the open socket to the gateway server with IP

    # on port 1883. 29 bytes of data are sent. The sent data represents

    #a MQTT-SN CONNECT query to the Cloud of Things gateway server. This should

    #be acknowledged by the server by sending a CONNACK (hex: 030500). The data

    #should be sent as usual in the hex string format. Exchanging <IMSI> and <PW> by

    #one of your valid IMSI/Password combinations, formatted in hex strings, should

    #result in the described behavior. at+nsost=0,””,1883,29,”1D0404010384<IMSI><PW>”



    Unfortunatelly it was not possible to connect to the server via command: at+nsost=0,””,1883,29,”1D0404010384<IMSI><PW>” It works neither with hexadecimal converted strings, nor the IMSI and PW as ASCII. We don’t know what should stay istead of <IMSI><PW> What should be entered in there? In response, we always got only one error and we tried pretty much all variants, whether converted, normal, with <> or without etc …

    Can you explain in simple words how to build the command set that works?

    Currently I have the feeling that in principle a connection can be established otherwise the previous registration steps would have already failed and thus we have network coverage in Tettnang - which is very good. Unfortunately, it has not been possible to register yet.

    I’m looking forward to a quick help 🙂

  • Deutsche Telekom IoT


    Your log file makes it clear that you are not connected to the cloud of things. As I mentioned in my first post, you need to get a CONNACK packet after sending the CONNECT command. The CONNACK packet consists of 3 bytes (0x030500 - see MQTT-SN specification!). However, after sending the CONNECT packet, you will receive a packet with a length of 2 bytes in your log. This can be recognized by the answer
    However, you do not have this answer in the log as described in the Quick Start Guide with the command

    Only then you know what the server has answered. However, I suspect that this is a DISCONNECT package (0x0218). This indicates a mistake. In such a case please check again whether you are using the correct IMSI / password combination. If this is the case I would ask you to contact me by e-mail (see profile), so that we can investigate the problem.